Question:
How mnay 3-digit numbers can be constructed from the digiits 1, 2, 3, 4, 5, 6, and 7 if each digit may be used:
a. As often as desired: 343
b. Only once: 210
c. Once only and the number must be odd?
I couldn't do C, I'd assume that you divide 210 by 2 to get 105. But the answer is 120, what am I missing out here?
Thanks.
+118608 Hi Guest,
I really like that you have explained what you did :)
Lets take a look.
Question:
How mnay 3-digit numbers can be constructed from the digiits 1, 2, 3, 4, 5, 6, and 7 if each digit may be used:
a. As often as desired: 343
Lets do units*tens* hundreds
7*7*7
b. Only once: 210
There is no zero so any digit can be anywhere.
7*6*5
I couldn't do C, I'd assume that you divide 210 by 2 to get 105. But the answer is 120, what am I missing out here?
c. Once only and the number must be odd?
The units this time can be 1 or 3 or 5 or 7 That is 4 possibilities
So that is 4*6*5 = 120
does that help?
